Python-GMP

Python extension module, gmp, providing safe bindings to the GNU GMP (version 6.3.0 or later required). This module shouldn't crash the interpreter.

The gmp can be used as a gmpy2/python-flint replacement to provide integer type (mpz), compatible with Python's int. It includes few functions (factorial, gcd and isqrt), compatible with the Python stdlib's module math.

This module requires Python 3.9 or later versions and has been tested with CPython 3.9 through 3.14, with PyPy 3.11 and with GraalPy 24.2. Free-threading builds of the CPython are supported.

Releases are available in the Python Package Index (PyPI) at https://pypi.org/project/python-gmp/.

Warning on --disable-alloca configure option

Most GMP packages enable using alloca() for temporary workspace allocation. This module can't prevent a crash in case of a stack overflow. To avoid this, you should compile the GMP library with '--disable-alloca' configure option to use rather the heap for all temporary allocations.

Published on the PyPI binary wheels aren't affected by this issue.

Warning on using mp_set_memory_functions()

This extension customize memory allocation routines, used by the GMP. Don't import it together with other GMP bindings, like the gmpy2.

Motivation

The CPython (and most other Python implementations, like PyPy) is optimized to work with small integers. Algorithms used here for "big enough" integers usually aren't best known in the field. Fortunately, it's possible to use bindings (for example, the gmpy2 package) to the GNU Multiple Precision Arithmetic Library (GMP), which aims to be faster than any other bignum library for all operand sizes.

But such extension modules usually rely on default GMP's memory allocation functions and can't recover from errors such as out of memory. So, it's easy to crash the Python interpreter during the interactive session. Following example with the gmpy2 will work if you set address space limit for the Python interpreter (e.g. by prlimit command on Linux):

>>> import gmpy2
>>> gmpy2.__version__
'2.2.1'
>>> z = gmpy2.mpz(29925959575501)
>>> while True:  # this loop will crash interpter
...     z = z*z
...
GNU MP: Cannot allocate memory (size=46956584)
Aborted

The gmp module handles such errors correctly:

>>> import gmp
>>> z = gmp.mpz(29925959575501)
>>> while True:
...     z = z*z
...
Traceback (most recent call last):
  File "<python-input-3>", line 2, in <module>
    z = z*z
        ~^~
MemoryError
>>> # interpreter still works, all variables in
>>> # the current scope are available,
>>> z.bit_length()  # including pre-failure value of z
93882077